Chocolates are not enough

Looked at in plain economic terms, the tariff cuts on some 28 manufactured goods and 47 agricultural products announced by Japan last week will mean relatively little in the way of new imports for that nation. By one measurement, imports could grow by about $380 million. But the US trade deficit with Japan this year is expected to reach a whopping $19 billion. Some trade concessions!

Still, the symbolic importance of lowering tariffs on a broad range of items should not be lightly dismissed. When it is recalled that Japan made tariff reductions on some 240 other products earlier this year, it is apparent that Tokyo is now acutely aware that its long-range prosperity necessitates reaching some form of compromise with its trading partners about gradually easing its numerous tariff charges and customs restrictions.

Certainly Japan has reason for doing so as quickly as possible. As an island trading nation, Japan is dependent upon an expanding and flourishing world trading system. Yet, while Tokyo has skillfully penetrated foreign markets with its admittedly excellent products, it has continued to protect its own large consumer market from the products of other nations. Such a one-way concept of trade cannot be justified, especially at a time when most industrial nations are facing deep recession and job layoffs.

It is questionable whether the US Congress will look upon the latest easing in tariff restrictions as evidence that Japan is at last moving away from protectionism. The lawmakers have been considering ''domestic content'' legislation that would require a substantial percentage of Japanese-made cars to be produced in the US - a law that if enacted would strike right at the heart of Japan's global primacy in auto production. Japan, not surprisingly, has been concerned about the enactment of such legislation - a concern that doubtless figured in the latest trade concessions.

What frustrates American traders is that Japan's liberalization seems to come in dribs and drabs - and reluctantly. It is interesting to note that the most important tariff concessions made by Japan this past week - those involving imports of tobacco, chocolates, and biscuits - came only after several days of haggling in Toyko and separately from the other 72, more modest, tariff reductions. And Japan still has not taken any steps to expand import quotas for beef and citrus products, as repeatedly sought by the US.

President Reagan should be candid with Japanese Prime Minister Yasuhiro Nakasone about the dangers of Japan's restrictive trade measures when they meet in Washington in mid-January. The two nations have become important trading partners. Every step should be taken to nurture that vital and mutually beneficial relationship.